Glutathione and Jasmonic Acid Biosynthesis Coordinate Antioxidant and Hormonal Responses to Alleviate Lead Toxicity in Pogonatherum crinitum Roots

Multiomics is increasingly valued as a strategy for investigating the regulatory mechanisms by which plants respond to adverse stress conditions. Currently, information on the molecular processes underlying plant responses to Pb stress, particularly those observed through an approach that combines proteomics and metabolomics, is lacking. Therefore, in this study, we aimed to explore functional correlations between Pb-responsive proteins and metabolites under Pb stress by performing label-free quantitative proteomics and untargeted metabolomics on the roots of the Pb hyperaccumulator Pogonatherum crinitum (Thunb.) Kunth. The selected Pb stress-responsive proteins were functionally verified using quantitative reverse transcription polymerase chain reaction (RT-qPCR) and parallel reaction monitoring (PRM). Under Pb stress, 397 upregulated and 431 downregulated proteins were identified through proteomic analysis. Metabolomic analysis identified 478 upregulated and 354 downregulated metabolites. Pathway enrichment analysis using the Kyoto Encyclopedia of Genes and Genomes revealed that differentially expressed proteins and metabolites were involved in pathways linked to heavy metal stress, such as starch and sucrose metabolism and plant hormone signal transduction. Through integrated proteomic and metabolomics analyses, we uncovered the coordinated regulatory interplay between glutathione (GSH) metabolism and jasmonic acid signaling. GSH reductase and 12-oxophytodienoate reductase drive the accumulation of GSH and jasmonic acid, respectively. The synergistic enhancement of these components is critical for maintaining cellular redox homeostasis and activating hormone-mediated defense signaling. These downstream metabolites were upregulated under Pb stress. RT-qPCR validation revealed that the transcriptional change trends were consistent with those of the proteomics analysis. Further quantitative validation of the target protein using PRM revealed significant upregulation under Pb stress. In conclusion, the P. crinitum root system upregulated the activity of key enzymes in the antioxidant system and plant hormone synthesis under Pb stress, thereby regulating the accumulation of GSH, glutamate, and metabolites for jasmonic acid synthesis. This integrated regulatory network provides promising candidate targets for breeding Pb-tolerant hyperaccumulators to remediate Pb-contaminated farmland and mining soil.